Generally, this invention relates to working seals between relatively rotating machine elements and in particular relates to an arrangement for automatically equalizing pressure on opposite sides of the seals regardless of which side of the seal is subjected to a relatively rising or lowering pressure. More particularly, this invention is an improvement of the sealing arrangement disclosed in the Federal Republic of Germany Patent No. 21 61 845.
For many applications of ball and roller bearings it is necessary to seal the relatively moving or working surfaces against outside contaminants. For this purpose the prior art has utilized seals in which there are small holes or labyrinths so that pressure equalization takes place under all operating conditions without the necessity of having continuous large openings. In such or similar embodiments, the vent openings can easily become clogged by dirt and grease residues. As will hereinafter be seen, this danger is not present in the case of sealing means constructed in accordance with the instant invention since in the latter pressure equalization takes place where there is always relative movement between the sealing lips and the mating travelling surfaces. This prevents dirt buildup.
For some applications, for instance in oillubricated gears, a further sealing element must be provided with oil behind the bearing which is sealed off on both sides. With previously known sealing arrangements it was not possible to provide a sufficient supply of oil since targeted conveyance of oil through the bearing was not possible. As will hereinafter be seen, with the oriented sealing lip arrangement of the instant invention, a further sealing element is not required for oiling in that the sealing lips convey small amounts of oil during the short periods the sealing lips lift off from the mating travel surface as a result of pressure changes. During these short periods of seal lift-off, oil is transported in a purposeful manner from one seal element to the other and through the elements, such as gears and bearings, in the space between these seal elements. In this case, the sealing elements perform a filtering function, by blocking movement of dirt particles thereby increasing bearing life.